Micropumps are used as cooling pumps for small electronic devices like notebook computers, or fuel transportation pumps for fuel cells. A micropump is a pump using a piezoelectric actuator which undergoes bending deformation in a bending mode by application of a voltage. The micropump has a relatively simple structure, with a reduced thickness as compared with the thickness of a pump using a motor as a drive source, and with low power consumption.
Patent Document 1 discloses a micropump in which a pump chamber is formed in a pump body, a piezoelectric actuator is attached onto a back surface (upper surface) of a diaphragm defining a top wall of the pump chamber, and an intake-side check valve and a discharge-side check valve are arranged directly below the pump chamber. This micropump has a structure, in which the pump chamber is located directly above the check valves, and the diaphragm and the piezoelectric actuator are arranged on the pump chamber. Hence, the thickness of the micropump is increased, thereby being disadvantageous in the reduction in thickness.
Patent Document 2 discloses a micropump in which a diaphragm defining a pump chamber, an intake-side check valve, and a discharge-side check valve are arranged in a plane. This micropump can be reduced in thickness as compared with the thickness of the micropump disclosed in Patent Document 1. However, since the diaphragm, and valve portions of the intake-side check valve and discharge-side check valve are formed of separate members. Hence, the number of components is increased, and the manufacturing cost is increased. In particular, when the check valves have umbrella structures having shaft portions and hood portions, the structures are complicated, resulting in the manufacturing cost being further increased.
Patent Document 3 discloses a diaphragm pump in which a valve portion of a check valve and a diaphragm portion are integrally formed. With this diaphragm pump, a coupling rod mounted to a motor via an eccentric shaft is coupled to a boss protruding from a back surface of the diaphragm portion. Also, ribs are provided between the valve portion and the diaphragm portion and at a peripheral edge, so as to prevent air from leaking. The valve portion and the diaphragm portion are formed of a single elastic member; however, it is necessary to mold the ribs and the boss in three dimensions, resulting in the cost being increased, and the thickness being increased. Further, since the drive source of the diaphragm portion is the motor, the thickness of the pump is large, and power consumption is high. Thus, the pump cannot be applied to a small electronic device.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-214349    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-337068    Patent Document 3: Japanese Examined Utility Model Registration Application Publication No. 61-36787